docs: def _quick_and_dirty_glyph_is_empty(font, glyph_name):
      """
      This is meant to be a quick-and-dirty test to see if a glyph is empty.
      Ideally we'd use the glyph_has_ink() method for this, but for a family of
      large CJK CFF fonts with tens of thousands of glyphs each, it's too slow.
  
      Caveat Utilitor:
      If this method returns True, the glyph is definitely empty.
      If this method returns False, the glyph *might* still be empty.
      """
      if 'glyf' in font:
          glyph = font['glyf'][glyph_name]
          if not glyph.isComposite():
              if glyph.numberOfContours == 0:
                  return True
          return False
      elif 'CFF2' in font:
          top_dict = font['CFF2'].cff.topDictIndex[0]
      else:
          top_dict = font['CFF '].cff.topDictIndex[0]
      char_strings = top_dict.CharStrings
      char_string = char_strings[glyph_name]
      if len(char_string.bytecode) <= 1:
          return True
      return False